Process for making mirrors or reflectors



H. K. HITCHCOCK PROCESS FOR MAKING MIRRORS OR REFLECTORS Filed NOV. 1'7 1923 5 Sheets-Sheet 1 INVENTOR H. K. HITCHCOCK Oct. 19

PROCESS FOR MAKING MIRRORS OR REFLECTORS Filed NOV. 17 1923 5 s t s t 2 INVENTOR Oct. 19, 1926. 1,603,951

H.- K. HITCHCOCK PROCESS FOR MAKING MIRRORS OR REFLECTORS Filed NOV. 7, 1925 s Sheets-Sheet s WWW? INVENRTOR jug/$ M 0a. 19, 1926. r 1,603,951 H; K. HITCHCQCK PROCESS FOR MAKING .MIRRORS OR REFLEGTORS Filed Nov. 17,1923

5 Sheets-Sheet 4 INVENTOR Oct. 19, 1926. 1,603,951

H. K. HITCHCOCK PROCESS FOR MAKING MIRRORS OR REFLECTORS Filed Nov. 17, 1 5 SheetsSheet 5 INVENTOR Patented Oct. 19,1926. A

UNITED STATES PATENT OFFICE- HALBEBT n. nrrcncocx, or PITTSBURGH, PENNSYLVANIA, assre'non 'ro rrr'rsnunen PLATE GLASS COMPANY, A conromrron on PENNSYLVANIA. v

PROCESS FOR MAKING MIRRORS OR REFLECTOBS.

Original application filed March 8, 1919, Serial No. 281,558. invaded and this application filed November 17, 1923. Serial No. 675,417.

.The invention relates to the process for making mirrors or reflectors. The invention is illustrated as applied to convex concave reflectors or lenses such as are used in search light or light house work and .has its greatest utility in. such connection, but the invention is not limited to such reflectors and is applicable to reflectors or mirrors of all types. Present application constitutes-a division of application Serial No. 281,558 filed March 8th, 1919, such application being directed to the mirror or reflector itself. The invention has to do primarily with the plating for protectin the silvering and its method of applicatlon, and its principal objects are (1) the provision of an improved method for applying the plating, and (2) the provision ofimproved means for supporting and handling the glass plate during the coating. operations.

The mirrors or reflectors for use in lighthouse and search light usefoften approximate five feet in diameter and it has been common to protect the silvering by plating a coating of metal, such as copper, over the silvering. This plating protects the silvering and prolongs its life, necessarily been made very thin and even when relatively thin has a tendency to become loosened and peel off with the silvering. This is due to the fact that a high tension is created in an electroplated coating, in some cases approaching the tensile strength of the metal, and this pull of the plating tends to loosen the silvering. The pull 'of the plating upon the silvering is directly proportional to the thickness of the plating and since the silvering is maintained on the glass only by-adhesion, the plating has heretofore been made so thin as to only imperfectly perfonm-its protecting function.

The purpose of the present invention is to provide a plating construction and means for applying it, whereby the plating may be made of any desired thickness and attached positively and secure? so that it cannot become loosened. Brie y stated, this result is secured by providing a reinforcing and attaching band of metal upon the edge of the reflector or mirror Jowhich the plating on the back of the silvering is secured. By the term e e, as used here, and in the claims, is

meant t e surface extending transversely of the back of the reflector such as the surface I 30 of Fig. 3. With this construction, any

but heretofore has tain embodimentstain forms of apparatus for carrying out the diagrammatic showing strain imposed by the shrinkage of the plat ing is taken by the reinforcing band, so that there is no tendency to loosen the silvering. By this means a coating may be applied of such thickness as to form a perfect protection against. injury to the silvering. The band upon the ed e of the mirror is preferably secured by e ectroplating a relatively thick coating of metal over such edge before applying the plating to the back, but such band may, if desired, be provided by shrinking or otherwise securing by mechamcal process, a ring of metal around the edge. In carrying out the process a glass sheet which is to be coated 1s preferably supportported in this manner is carried from one.

bath to the other and successivelv lowered .in such baths, a silvering coating eing first deposited, and subsequently an electrolytic coating or plating. In case the supporting or reinforcing band is to be electrically deposited, such coating is deposited in the electroplating bath before depositing the plating upon the back of the plate. After a relatively thick band of metal has been deposited upon the edge of the plate, the current'is so directed through the bath that a plate is deposited both upon the back and upon the edge, thus securing the plating upon the back to that upon the edge. Cerof the invention and cerprocess are illustrated in the accompanying drawings, wherein: g

Figure 1s a plan view showing the-general arrangementof the apparatus. Fig. 2'

'is a partial vertical section through a part of the apparatus of Fig. 1 and a partial he electric connections employed. Fit" larged detailed sections taken through the edge of the reflector of Fig. 2 and-show .mg

the means for preventingacces's of'the liquid of the bath to the concave interior of the reflector. .Fig.5 is an enlarged section on thelin VV'of Fig. 2. Fig. 6 is a vertical section through modified form of apparatus and illustrates the step of coating theban'd upon the edge of the reflector. Fig. 7 isa verticalsection show- Iland' 4 are ening the step of coating the back of the reflector following the step of coating the edge as illustrated in Fig. 6. Fig. 8 is a vertical section through still another form of apparatus which may be employed in carrying out the process. Fig. 9 is an enlarged vertical section through the edge of the reflector and supporting device as illustrated in Fig. 8. Figs. and 11 are sections through a completed reflector, Fig. 11 being an enlargement at the edge of the construction of Fig. 10. Fig. 12 is an enlarged section through a modified reflector construction, and Figs. 13 and 14 are sections through still another type of reflector, having an opening through its central portion, Fig. 14

' bath 1, which may being an enlarged section at the center of the reflector of Fig. 13.

Referring first to the. construction shown in Figs. 1 and 2, 1 is a silvering bath; 2 is an electroplating bath; 3 is a truck carrying transversely thereof a vacuum frame 4 provided with the three vacuum lifting cups 5, 6 and 7, and 8 is the track upon which the truck is mounted to move, so that the reflector may be carried from one bath to the other, first receivin the silvering coating in he the last one of a series of baths for securing the silvering treatment,

and then receiving the electrical coating in the bath 2.

The truck 3 comprises a framework 9 mounted upon the wheels 10 and provided at its upper portion with a bearing member 11 upon which the frame 3 is pivotall mounted on shaft 12. The frame 3 is pre erably counterweighted, as indicated at 13, and is swung about at the shaft 12 by means of a worm 14 and gear 15 co-operating therewith, the worm 14 being turned by means of the handle 16. v

The vacuum cups 5, 6 and 7 are carried by .a Y-shaped frame 17, secured at one end to the beam 3 by means of the angle clip 18, and secured at its other end to sucli beam by means of the adjusting device illustrated in Fig. 5. This device comprises a pair of threaded rods 19, secured at their lower ends to the frame 17 and passing at their upper ends through the transverse plate 20, se-

cured to the beam 3 by means of the clip 21.

Wing nuts 22 are provided on the upper ends of the rods 19 and springs 23 provide a pressure tending to move the frame 17 downward. The foregoing construction provides a means whereby the reflector carried by the beam may be leveled up so that when placed in the bath of liquid, the level of-the liquid will be at. the same point throughout the circumference of the reflector. The spring in the clip 18-permits the frame 17, carrying the vacuum cups, to be moved up and down a limited amount around this clip as a pivot, and the adjustable rods 19, with their wing nuts 22, permit the other end of the frame 17 to be adjusted up or down the slight amount necessary to bring the upper edge of the reflector into a horizontal plane.

Inorder to prevent the liquid from the bath verflowing into the interior of the reflecto when the reflector is pushed down into the bath, so that the liquid rises above the edge thereof, the annular sealing member 26 is employed. This member may be of either wood or metal, and is provided On its lower edge with'what may be termed an annular cup, such cup consisting of an annular recess in the member 26, in which is mounted the rubber strip 27. The rubber strip 27 is secured by means of the metal strip 28 (Fig. 3'), held by screws, and air may be exhausted from the lower side of the strip through the pipe 28* (Fig. 4).- When air is exhausted in this manner from the annular vacuum cup, the member 26'is pulled down tightly against the inner surface. of the plate 29 so that the liquid in the bath may rise above the edge 30 of the plate without leaking into the interior of the reflector. Having the level of the liquid extend a slight distance above the edge 30 insures that this entire edge shall be coated, even though the edge 30 should notbe entirely true throughout its entire circumference, and though its yertical position should vary slightly. This sealing member 26 is useful not only in the plating operation in the bath 2, but also in the silvering operation which occurs in the bath 1 and other preliminary baths preceding the bath 1 and not shown.

The plating bath is preferably constructed as illustrated in Fig. 2, and comprises a tank 31 containing the liquid 32 and having a circulating pump 33. The purpose of the pump is to secure a flow of liquid over the surface of the reflector, thus removing bubbles and giving a more uniform deposit. The overflow from the tank is received in a trough 34, having an outlet pipe 35 leading to the tank 36, the pipe 36 inlet to the pump and 37 the outlet therefrom. The pipe 35 discharges through the filler 38in order to remove impurities from the liquid, and the bath itself is provided with a filtering fabric 39, through which the pipe 37 extends. The bath is provided with two anodes, one of which, 40, lies at the upper edge of the bath and comprises anannular band, while the other of which, 41, is in the form of a dished perforated 'member'or grid of copper or brass lying below the fabric 39 and following the contour of the reflector. The cathode consists of the silver plating on the back'of the mirror andis connected to the battery or source of current by a strip of metal 42 (Fig. 3), which extendsv around the edge of the member 26 and is fastened thereto by means of screws 43. This strip 42 is preferably of copper or constituting the brass and engages the silvering on the edge ;of the glass sheet. Preferably this strip 42 is silvered in the silvering bath at the same time that the silvering is applied to the back and edge of the reflector, so that a good contact between the strip and the silvering is insured. Electrical contact is made by means of a plurality of copper or brass springs 44 secured to the member 26 and engaging the top of the band 42, which servealso to keep the ring in contact with the edge of the mirror.

' The electrical apparatus and connections comprise the source of current 44, the wire the reflector.

45 leading to the two switches 46 and 47, the wires 48 and 49 leading to the anodes 40 and 41 and the return wire 50 leading from the band 42 to the source of current 44.

The operation of coating the convex side of a reflector is as follows. The plate is secured upon its concave side to the vacuum cups 5, 6 and 7 and the convex face of the reflector is dipped int-o the bath 1, this dipping beingto such depth that the edge 30 (Fig. 3) of the reflector is silvered as well as the convex surface. The truck is then moved to the position of Fig. 1 and the reflector lowered into the hat-h occupying the position illustrated in Fig. 2. At this time the level of the liquid is slightly above the extreme upper edge of the plate 29. The switch 47 is now closed so that a flow of current passes through the liquid from theanode 40. to the silvered-edge 30 and a deposit of metal from the bath, such as copper, is secured upon such edge 30. Thisdeposit is continued-until a relatively thick strong band of copper is secured upon the edge of the reflector. Atthis time there is a certain amount of deposit upon the back of the reflector adjacent the edge 30, but this deposit is relatively slight and there is practically no deposit upon the main portion of the back of the reflector. After this band of metal has been deposited upon the edge of the reflector, the switch 46 is closed, so that the current passes to the anode 41 and thence through the liquid to the silvered back of This flow of current is continued until the necessary thickness of deposit is secured. If desired, successive coats of plating may be applied both to the edge and to the back of the reflector.

Fig. 12 of the drawing illustrates the deposit of plating upon the edge of a reflector as a result of the procedure above described,

the edge of the reflector in this case being Over the back of the reflector and terminating at the point 54 is a coating ofvarnish 55, and over this coating of varnish is a. woven metal fabric 56, which extends over the back of the reflector and-over the edge thereof as illustrated. After this fabric is applied, the. reflector is returned to the plating bath and an edge plating 57 is applied, such edge plating extending around to the point 54 and serving to securely anchor the metallic fabric in position. A further coating of varnish 58 is then applied, extending over the hack to the point 54.

Figs. 6 and 7 illustrate a modified method of procedure, In the construction here illustrated, 59 is the tank, 60 is a shaft rotated from the belt 61, 62 is the reflector to be coated, carried at the upper end of the shaft, 63 is a metal plate carried in the plating bath, and 64 is a contact plate engaging a contact weight above the upper end of'the shaft 60. Current is supplied from a bat tery 65, which has connection with the plates 63 and 64. After the back and edge of the reflector have. been silvered, the parts are positioned as illustrated in Fig. 6, and a relatively heavy hand of metal is placed uopn the edge of the reflector, asindicated at 56, the shaft 60 being revolved. in order to secure the removal of any bubbles from the edge of the reflector and to give a uniform deposit. After the plating of the edge, the reflector is inverted, as indicated in Fig. 7,,and an annular member 67, provided with a groove 68, is applied in the manner illustrated, the member 67 being carried by shaft 68 so that the reflector ma be rotated. The groove 68 is provided with an electric conducting wax so that when the reflector is pushed down to'the position il-' lustrated, the wax in the-groove 68 contacts with the plated edge 66 with sufficient force to give a rotation'of the reflector when the annular member 67 is rotated. -An electrical connection is made to the shaft 68- so that when current is applied to the plate 63 and taken from the shaft 68 as indicated, being the source of. current, a flow of current through the bath is secured, thus plating the convex surface of the reflector. The depth to which the reflectoris placed into carried and rotated from the shaft 70, set

at an angle to the bath in the tank 71. The

shaft 70 isprovided with a framework 71, having a plurality of suction cups 72, such suction cups being of any desired approved .type, and being operated through the pipes Around theedge of the reflector is a reinforcing band or rod 77, and the metallic wax 76 makes contact with this band and with the upper edge of the reflector, as illustrated in Fig. 9. When the reflector is rotated in the position illustrated in Fig. 8, and current is applied to the anode 78 and to the'strip 75, lying behind the .metallic wax, a flow of current through the bath is secured and a deposit of metal upon the back of the silvering 7 9 is secured. This deposit of metal extends up around the edge of the reflector and anchors the reinforcing member 77 in position. This gives a reinforcing at the edge of the reflector consisting partially of the deposited metal and partially of the annular member 77. If a heavier deposit of metal upon the edge of the reflector is desired, this may be secured by raising the shaft 70, with respect to the bath, until the edge of the reflector extendsinto the liquid only a slight distance. If now the coating action is allowed to continue for a while longer, an additional deposit is secured upon the edge of the reflector and extends only a slight distance over the back of the reflector.

Figs. 10 and. 11 illustrate a reflector construction in which the band. 80 at the edge of the plate 81 is formed separately and placed upon the reflector instead of being plated upon the reflector, as heretofore described.- As shown in Fig. 11, 82is the silvering, and after this coating and the band 80 have been applied, the plating coating 83 oficopper is applied, as heretofore described. This coating extends over the back of the reflec tor and also over the metal band'SO, so thatthe plating at the back is securelyattached-to the edge band. After the plating hasjbeenapplied,'the varnish coat 84 is applied,'extending to the point 85. Over this coating the metalfabric 86 is placed, such trated in Fig. 14

[subscribed my name this 15th day vember, 192

fabric extending around over the edge of the reflector and being secured in place by the plating 87 which extends up to the point 88. A final coating of varnish 89 is then applied over the metal fabric on the back of the reflector.

Figs. 13 and 14 illustrate the invention as applied to a reflector having the opening 90 through the center. The construction at the outer edge of the reflector is the same as heretofore described in connect-ion with Figs.

10 and 11, but the reinforcing around the opening 90 is somewhat different, as illus- As here shown, 91 is the silvering coating and between this coating and the metal ring 92a layer 93 ofwax is introduced. This cushions the ring and takes care of thedifference in expansion and contraction between the ring 92 and the glass plate 94. The plating 95 of copper or other metal is applied over the silvering at the back of ,the reflector and over the ring 92, as in the construction heretofore described. The protecting coatings of metal fabric and varnish are applied as in the other types of construction.

What I claim is: 1.- The process of electroplating a reflector which con'sists'in silvering the back and edge of a glass plate, depositing a band of metal upon said edge by electrolysis, and then depositing a metal coating by electrolysis on said back and extending over said band.

2. The process of electroplating a concave convex glass plate which consists in silvering the convex surface of the plate and its edge, supporting the -3. The process of electroplating a reflector which'consists in silvering of a glass plate, and depositing a coating of metal upon the sllvere the back and edge rotectin back an edge of the plate byelectrolysis so that thecoating on theed e is-irelatiyely heavy and constitutes an anc oring and for the plating'on .the back of the plate.

Intestimony whereof, I have 'llGIfGllfiitO HALBEBT K. HITCHCOCK.

plate in an electroplating bath with its convex surface down and with bet-ween the silvering on the securing means f 

